In a rechargeable battery pack or other electrical energy storage devices, it is necessary to know the amount of charge left to determine the electrical energy lifetime. Current solutions solve this problem by doing precise measurements of the voltage across the electrical energy storage device, the charging and discharge current from the electrical energy storage device, the ambient temperature, the electrical energy storage device chemistry and then use an algorithm to predict the state of charge (SOC) of the electrical energy storage device. The current solutions consume substantial amounts of power due to the utilization of analog-to-digital converters (ADCs), clocks and other circuitry. Ideally the voltage and current should be monitored continuously. However, current systems sample the voltage and current by taken a series of repeated samples to mitigate samples that include current surges.